Showthread Question Mark
When the thread ID is not passed to the wiki URL generator (e.g. from a wiki link BB-Code), and the thread is not a wiki URL, or the wiki forum is not set to wiki for some reason, the URL will be in the form showthread.php?t=, with nothing after it. This will lead to an error/404.
This isn't entirely fixable, but I've tried to add a failsafe for the next build. Since this mainly happens for wiki links (a showthread link should have the thread ID available), the failsafe will assume it's a wiki link to a page in the Default space. If the Default space is not wiki-enabled (which would throw its own error by the way), it should degrade nicely to a factory-default wiki URL. This would still lead to an error/404, but at least the URL is more useful.